In an evolved packet system (EPS for short), user equipment (UE for short) is connected to an evolved NodeB (eNB for short) by using a Uu interface, and accesses a network by using the eNB.
The eNB is connected to a mobility management entity (MME for short) by using an interface, and is connected to a serving gateway (Serving GW for short) by using another interface. The MME performs mobility control on the UE, and the serving gateway mainly routes and forwards a data packet for the UE.